The present invention relates generally to a binding unit which binds a plurality of sheets in adherence to a binder.
FIGS. 23 and 24 show a conventional binding unit. The binder 40 used in this binding unit 46 includes an electric heater 42 and an adhesive layer 43 covering the heater 42 over the inner surface of its spine 41. Electrodes 44 of a pair are provided on either end of the electric heater 42, and are exposed on the outer surface (the lower surface in the figures) of the spine 41.
The binding unit 46 includes a container 47 into which the binder 40 is loaded. A pair of electrode terminals 48 which come into contact with the electrodes 44 of the binder 40 is provided on the inner surface of the bottom of the container 47 whereby electric current is supplied to the electric heater 42 through the electrode terminals 48.
In order to bind sheets, the binder 40 is loaded into the container 47, and electric current is supplied to the electric heater 42 through the terminals 48 and electrodes 44. As a result, the adhesive layer 43 heats and melts, and one side of the stack of sheets 45 is adhered to the binder 40, whereby the stack of sheets 45 is bound.
For the purpose of sufficiently heating and melting the adhesive layer 43 in the conventional binding unit 46, it is important that the electrodes 44 of the binder 40 and the electrode terminals 48 be securely in contact with each other when the binder 40 is loaded in the container 47. Should foreign material such as dust or paper powder, however, enter the container 47 through the insertion opening for the binder and stick to the electrode terminals 48, defective contact might occur between the electrodes 44 of the binder 40 and the electrode terminals 48, leading to uneven or insufficient heating of the adhesive layer 43.
Particularly, when the binding unit 46 is provided in a copying machine and has the insertion opening directed upward, foreign material is liable to enter the binding unit 46 through the opening. Such foreign material remaining inside the binding unit 46 is impractical to remove.
Furthermore, a binding unit provided in a copying machine as disclosed in Japanese Utility Model Laying-Open No. 41261/1986 or Japanese Utility Model Laying-Open No. 121456/1986, is not allowed sufficient space for suitable mounting due to its positional relation to other elements, such as a sorter, or vent holes provided in a side wall of the machine body. Stable support of large-size sheets in the binder unit 46 is difficult in consequence, and an operator is left to support the sheets by hand in order to bind them reliably.